Method and device for regulating the tension and length of a sheet of material

ABSTRACT

A sheet of material passing from an upstream operating station to a downstream operating station is regulated as to its tension and length by a pair of jockey rollers one on each side of a drum, one roller being biased against the sheet and the other being free but controlled in position by a servo-mechanism from the first roller, the second roller by its position controlling the speed of cylinders at the upstream station.

United States Patent Corse July 1, 1975 [5 METHOD AND DEVlCE FOR REGULATING 2,586,286 2/1952 Andreas 226/44 x THE TENSION AND LENGTH OF A SHEET 3,587,959 6/1971 Glover 226/44 X 3,625,447 12/1971 Hank 226/44 X OF MATERIAL [76] Inventor: gsgz g gg g i g Rodm Primary Examiner-Richard A Schacher Attorney, Agent, or FirmRobert E. Burns; [22] Filed: Jan. 9, 1974 Emmanuel J. Lobato; Bruce L. Adams [2i] Appl. No.: 431,979

[57] ABSTRACT [30] Foreign Application Priority Data A h t f I f s ee 0 materia passing rom an upstream operat- 1973 France 7300899 ing station to a downstream operating station is regu- [52] U S Cl 226/44 226/ 4 lated as to its tension and length by a pair of jockey [51] B65h 25/04 rollers one on each side of a drum, one roller being {58] Fie'ld 1 H3 H4 biased against the sheet and the other being free but controlled in position by a servo-mechanism from the [56] References Cited first roller, the second roller by its position controlling UNITED STATES PATENTS the speed of cylinders at the upstream station.

1,758,794 5/1930 Hoxie 226/44 X 5 Claims, 1 Drawing Figure 4 s ED 1 25. r R 9d 4 i i 7\ St: A r 1.1a

Sb (9! to a E 7: l 9e METHOD AND DEVICE FOR REGULATING THE TENSION AND LENGTH OF A SHEET OF MATERIAL BACKGROUND OF THE INVENTION The present invention relates to a device for regulating the tension of a moving sheet of material and for keeping its length constant, particularly in between a rotary press, and an apparatus downstream of the latter for shaping the printed sheet.

A device is already known for regulating the tension of a sheet of material between a delivery unit, situated downstream from the printing units, and a shaping unit. This device comprises a jockey roller which is caused by a tensioning device (weight or spring) to bear on the sheet. The tensioning device is integral with a lever which contacts a thrust, for which purpose the rate of output of the device is regulated manually. It has nevertheless been found that where sheets of a very light material are concerned, particularly light aluminium (having a thickness of 6-12 microns), the adjustment required is too fine to be coped with by an apparatus of this kind.

The object of the present invention is to remedy this drawback.

SUMMARY OF THE INVENTION In accordance with the invention, the variation in the length of the sheet, in one direction or in the other, leads to corresponding displacements of two jockey rollers which bear against the sheet, only one of the rollers being biased to counteract tension in the sheet. The rollers move along the arcuate surface of a drum over which the sheet passes. The tension variations undergone by the sheet are detected and compensated on the basis of the modifications occurring in the shape or position of the tensioning device of the biased roller. The position of the other and unbiased roller is varied, by means of a servo-control device, in accordance with the changes occurring in the shape and position of the tensioning device, in order to counteract the variations in the length of the sheet. The speed of the driven one of a pair of sheet-engaging cylinders upstream of the rollers and thus the delivery of the sheet is controlled in accordance with the change in the position of the unbiased roller.

A process of this kind regulates the tension in the sheet and maintains the length thereof constant without subjecting it to any stresses which might cause even momentary stretching to an unacceptable extent, a feature of particular value in connection with materials to be printed having comparatively inadequate limits of elasticity. Furthermore, it enables the tension in the sheet to be adjusted very finely.

The invention also relates to a device for the performance of this process.

DESCRIPTION OF DRAWING The drawing is a schematic diagram of the device provided by the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT The device according to this invention is associated with an apparatus, such as that shown in the drawing and including an upstream pair of cylinders A and a downstream pair of cylinders B, between which passes a sheet of material 4.

The upstream pair of cylinders A may be a delivery unit situated at the outlet from a rotary press and consisting of a lower driven cylinder I and an upper countercylinder 3, parallel and tangential to the first cylinder, while the downstream pair of cylinders B may consist of shaping cylinders 5, 6 of some kind or other, tangential to each other.

To ensure that the finishing of the sheet is effected under satisfactory conditions, the tension and the length of the sheet between these two pairs of cylinders A and B must be kept constant.

The stress compensation which balances out a varia tion of tension of the travelling sheet is provided by a first downstream jockey roller device including a group of parallel rollers 7a, 7b, ie an upper restoring roller in a fixed position, and a jockey roller 7b. A drum 7c is rotatable about an axis parallel to these rollers. A tensioning device 8 consisting of a counterweight as shown, or of a spring or any other similar means supplies, by deformation or by change of position, the stress required to equilibrate the tension of the sheet. A lever 7d constituting the support of the roller 7b and integral with an arm 7e bears the tensioning device 8. The lever 7d and the arm 7e are articulated to a horizontal shaft 11 about which the drum 7c rotates freely.

According to the invention a second, upstream jockey roller device 9 is provided associated with a sheet tensioning device of its own. It comprises a group of rollers parallel to the first-mentioned rollers i.e. an upper restoring roller 90, having a fixed position, and a jockey roller 9b. This upstream jockey roller 9b is not subjected to the action of a restoring counterweight or spring, guides sheet 4 from the upstream delivery unit A to the drum 7c, while with the downstream device 7 guides the sheet from the drum to the downstream receiving unit B. The said device 9 likewise comprises a lever 9d which constitutes a support for the jockey roller 9b and is articulated to the same shaft 11 as the lever 7d, independently of this latter.

The sheet of material 4 emerging from the upstream pair of cylinders A thus passes, in succession, over the restoring roller 9a, under the upstream jockey roller 9b over the upper half of the drum 7c, under the downstream jockey roller 7b, and over the downstream restoring roller 7a, to be taken up, finally, by the downstream pair of cylinders B.

The levers 7d and 9d are interconnected by a mechanical servo-control device 12, hydraulic or other, which imparts to the lever 9d a rotary movement about the shaft 11, in the same direction as that of the lever 7a, so that, whatever the movement of this latter about the shaft 1 l, the two levers form a prolongation of each other, without the upstream jockey roller 9b exerting any force such as to increase the tension of the sheet of material 4. Thus, if an increase of tension occurs in the sheet 4, immediately upstream from the pair of cylinders B, for example, then the downstream jockey roller 7b re-ascends, raising the tensioning device 8, so that the lever moment of the antagonistic force supplied by this latter increases by the same value, maintaining a constant tension in the sheet (position 7'b in the drawing). However, if the downstream jockey roller 7b were to move in this way without compensation, the length of the sheet 4 between roller units A and B would decrease to below the standard selected at the beginning of the operation, and this would impede the function of the apparatus. The servocontrol device 12 has been provided for the purpose of counteracting this variation in length. The lever 7d rotates about the shaft 11 by a certain angle a in the upward direction, to oc cupy the position shown in broken lines on the drawing. The other lever 9d, independent of the lever 7d as described, does not of itself follow the movement about the shaft 11. It follows such movement solely under the action of the servo-control device 12. This device, known by itself, causes the other lever 9a to rotate about the shaft 11 by the same angle a and in the same direction, until it forms a prolongation of the lever 7d, as shown in broken lines on the drawing, the second jockey roller then being promptly as well as accurately lowered into position 9'b. Thus, the first jockey roller 7d detects any variation in the tension of the sheet of material 4 and effects, by its displacement, the compensation of the said variation, by following any movement resulting in a shortening or prolongation of the sheet. Such displacement is transmitted, via the lever 7d and the servo-control device 12, to the lever 9d, which then moves in the same direction, taking with it the upstream roller 9b, in such a way as to lengthen or shorten the sheet 4 by a compensation length equal to the variation in length which it has undergone and to restore it to the normal length. Furthermore, the lever 9d is connected to a second arm 92 or any other control device of a mechanical or hydraulic nature, which transmits the prompt and accurate change of positions of lever 9d to a speed variator l controlling the rotation speed of the driven cylinder 1 of the upstream pair of cylinders A, to vary the output of the sheet 4 in accordance with the length variation detected. Thus, the delivery of the sheet 4 at the outlet side of the cylinders 1 and 3 is slightly increased, to enable the yielding jockey roller 9b, upstream, to descend to its position 9'b.

The device covered by the present invention obviously allows of numerous alternative embodiments within the spirit and scope of the invention as regards the tensioning device 8, the servo-control device 12, the control device for the speed variation and other items, but this in no way affects the principle of the invention.

I claim:

1. Apparatus for maintaining and regulating tension in a sheet of material, travelling from an upstream area to a downstream area, to keep the length of the sheet between said areas constant, comprising;

upstream sheet engaging means for delivering a travelling sheet; downstream sheet engaging means for receiving the delivered sheet; drive means for driving at least one of said sheet engaging means; a jockey roller unit disposed between the upstream and downstream sheet engaging means comprising a drum rotatable about an axis transverse of the travelling sheet and having an arcuate surface portion concentric with said axis and engageable with the sheet; upstream jockey roller means engaging the sheet to guide it from the upstream sheet engaging means onto an upstream part of said arcuate surface portion; downstream jockey roller means engaging the sheet to guide it from a downstream part of said arcuate surface portion to the downstream sheet engaging means; means for biasing one of the jockey rollers to maintain tension in the sheet engaged thereby; and

servo-control means for adjusting a position of the other jockey roller in response to a change of position of said one jockey roller and for thereby controlling said drive means to compensate corresponding variations of the length of said sheet between said upstream and downstream sheet engaging means;

whereby said compensating is performed both promptly and accurately.

2. Apparatus according to claim 1 including first and second levers, both pivoted about said axis of the drum and supporting, respectively, said downstream and upstream jockey rollers for movements along said arcuate surface portion.

3. Apparatus according to claim 2 in which said drive means is disposed for driving said upstream sheet engaging means, and said servo-control means is disposed for adjusting a position of one of said levers in response to a change of position of the other lever.

4. Apparatus according to claim 1 in which said upstream sheet engaging means is a cylinder unit of a press for imprinting the sheet of material.

5. Apparatus according to claim 4 in which said downstream sheet engaging means is a cylinder unit of apparatus for shaping the imprinted sheet of material. 1F k 

1. Apparatus for maintaining and regulating tension in a sheet of material, travelling from an upstream area to a downstream area, to keep the length of the sheet between said areas constant, comprising; upstream sheet engaging means for delivering a travelling sheet; downstream sheet engaging means for receiving the delivered sheet; drive means for driving at least one of said sheet engaging means; a jockey roller unit disposed between the upstream and downstream sheet engaging means comprising a drum rotatable about an axis transverse of the travelling sheet and having an arcuate surface portion concentric with said axis and engageable with the sheet; upstream jockey roller means engaging the sheet to guide it from the upstream sheet engaging means onto an upstream part of said arcuate surface portion; downstream jockey roller means engaging the sheet to guide it from a downstream part of said arcuate surface portion to the downstream sheet engaging means; means for biasing one of the jockey rollers to maintain tension in the sheet engaged thereby; and servo-control means for adjusting a position of the other jockey roller in response to a change of position of said one jockey roller and for thereby controlling said drive means to compensate corresponding variations of the length of said sheet between said upstream and downstream sheet engaging means; whereby said compensating is performed both promptly and accurately.
 2. Apparatus according to claim 1 including first and second levers, both pivoted about said axis of the drum and supporting, respectively, said downstream and upstream jockey rollers for movements along said arcuate surface portion.
 3. Apparatus according to claim 2 in which said drive means is disposed for driving said upstream sheet engaging means, and said servo-control means is disposed for adjusting a position of one of said levers in respoNse to a change of position of the other lever.
 4. Apparatus according to claim 1 in which said upstream sheet engaging means is a cylinder unit of a press for imprinting the sheet of material.
 5. Apparatus according to claim 4 in which said downstream sheet engaging means is a cylinder unit of apparatus for shaping the imprinted sheet of material. 